Idrija Mercury Mine Research Articles

Overview of existing information on important closed (or in closing phase) and abandoned mining waste sites and related mines in Slovenia

The presented work provides a comprehensive inventory of data on closed (or in closing phase) and abandoned underground and surface mines and mining waste sites in Slovenia, collected within the framework of the Geological Survey of Slovenia (GeoZS) over the last two decades. Furthermore, a detailed overview of information on closed and abandoned mining waste sites in Slovenia is given. In order to establish the inventory, a definition of the work methodology, a comprehensive research of the archived and published literature, and the harmonisation and management of the collected data was carried out. Based on a selected methodology, the inventory contains information on 33 metal mines, 43 coal mines, 51 non-metallic mineral resource mines, 156 waste sites from metal mines and 18 waste sites from coal mines. The inventory is in the open access Google Earth file. It provides a basis for further research into the environmental impact of mining waste, which has been carried out since the EU Directive on the management of waste from extractive industries (Directive 2006/21/EC hereafter) was adopted into national law. In general, about 11,621,333 m3 of waste sites from metal mines and 76,188,000 m3 of waste sites from coal mines are covering about 678 hectares of Slovenian territory. More than half (64 %) of the waste from metal mines was produced in the Mežica lead and zinc mine, while the other two mines with a still significant share of produced waste were the Idrija mercury mine (18 %) and the Žirovski vrh uranium mine (15 %). Among the closed coal mines, the largest amount (46 %) of waste was generated by the coal mine Trbovlje-Hrastnik, while the other two coal mines with still significant share of waste produced were Kočevje (28 %) and Kanižarica (17 %).

The chemical species of mercury accumulated by Pseudomonas idrijaensis, a bacterium from a rock of the Idrija mercury mine, Slovenia.

A mercury-resistant bacterial strain has been isolated from a rock of the Idrija mercury mine in Slovenia. The rock had 19 g carbon and 2952 mg mercury (Hg) per kg. Mass spectrometry and DNA sequencing showed that the bacterium belongs to the Pseudomonas genus. It is called Pseudomonas idrijaensis. This bacterial strain is sensitive to methylmercury (MeHg) like the reference P. aeruginosa strain PAO1, and is resistant to divalent mercury (Hg(II)) in contrast to PAO1. This difference could be attributed to the presence of the mer operon yet deprived of the merB gene encoding the organomercurial lyase, on the basis of whole genome sequencing. The P. idrijaensis mer operon displays the RTPCADE organization and is contained in the Tn5041 transposon. This transposon identified here occurs in other Gram-negative Hg-resistant strains isolated from mercury ores, aquatic systems and soils, including Pseudomonas strains from 15,000 to 40,000 years old Siberian permafrost. When P. idrijaensis was exposed to mercury chloride, two intracellular Hg species were identified by high energy-resolution XANES spectroscopy, a dithiolate Hg(SR)2 and a tetrathiolate Hg(SR)4 complex. P. idrijaensis had a much higher [Hg(SR)2]/[Hg(SR)4] molar ratio than bacteria lacking the mer operon when exposed to 4 μg Hg2+/L - resulting in an intracellular accumulation of 4.3 μg Hg/g dw. A higher amount of the Hg(SR)2 complex provides a chemical signature for the expression of the dicysteinate Mer proteins in response to mercury toxicity.

Do bacteria occupying important ecological niches contribute to the entrance of mercury into the food webs?

Bioavailable mercury represents a major threat locally to wildlife and also contributes to the global Hg pool and cycling of Hg. In this study, we focused on bacterial mobilization of inorganic Hg contained in sediment collected from the river Idrijca near the site of UNESCO's Idrija Mercury Mine. At the lowest trophic level, bacteria have an important role in Hg mobilization due to the cumulative nature of Hg in the food chain. Ignoring the most commonly studied sulfate reducing and methanogenic bacteria, we focused, among others, on the ubiquitous mineral weathering bacteria, Bacillus and Pseudomonas, the nitrifying Nitrobacter sp., the nitrogen fixing Rhizobium and Azotobacter, the aerobic Brevundimonas and the exoelectrogenic Schewanella to examine their potential for the mobilization of total (tHg) and the bioavailable Hg (bHg) fraction. We showed that several bacterial groups are able to mobilize the less soluble formes of Hg, i.e. HgS and smelting calcine in the sediment, either via close contact between cells and sediment particles or by the cell- excreted exudates resulting in increased levels of tHg and bHg in solution or in the cell biomass. The diversity of bacterial groups capable of mobilizing Hg implies that many different more general pathways and consequently many mobilization mechanisms, are possible apart from the Hg specific routes. In particular, the bacterial groups Pseudomonas and Bacillus, with their mineral weathering capabilities, were shown to be able to increase or decrease the availability of bHg depending on the peculiarities of their respective metabolisms and the nature of their exposure to the river sediment. Additionally, we showed that accumulation of Hg in the biofilm biomass is one type of mechanism influencing the bioavailability of Hg and can act as a point at which the insoluble Hg can enter into the foodweb.

Diurnal fluxes of gaseous elemental mercury from the water-air interface in coastal environments of the northern Adriatic Sea

A crucial step towards developing a more complete understanding of mercury (Hg) biogeochemical cycling in coastal environments is the measurement of the fluxes of gaseous elemental mercury (GEM), at the water-air interface (W-A interface). A floating flux chamber coupled with a real-time atomic adsorption spectrometer (Lumex-RA 915M) was applied to measure GEM concentrations, and to estimate the diurnal evasion flux at the W-A interface during three seasonal campaigns at four selected sites: two in a lagoon-based fish farm, one in an open lagoon environment highly impacted by long-term activities from the Idrija mercury mine (Slovenia), and an uncontaminated area of the Gulf of Trieste, the Bay of Piran (Slovenia). In this study, the regional background concentration measured at the uncontaminated site of atmospheric GEM (from 1.60 ± 0.95 to 2.87 ± 1.52 ng m−3) was determined. GEM fluxes at the W-A interface were found to be significantly higher during the summer (from 51.2 ± 8.8 ng m−2 h−1 to 79.9 ± 11.4 ng m−2 h−1) and correlated to incident solar radiation and water temperature. This finding confirms the importance of these two parameters in the photoreduction and biotic reduction of Hg2+ to dissolved gaseous mercury (DGM), which is volatile and easily released to the atmosphere in the form of GEM. These new insights will be of help for future estimates of Hg mass balance in one of the most contaminated areas in the Adriatic Sea.

Hg and CO2 emissions from soil diffuse degassing and fumaroles at Furnas Volcano (São Miguel Island, Azores): Gas flux and thermal energy output

Gaseous elemental mercury (Hg0g or GEM) and CO2 are emitted from active hydrothermal systems in volcanic areas mostly through diffuse degassing. Here, data from about 400 simultaneous measurements of soil GEM and CO2 flux performed within the caldera of Furnas Volcano, São Miguel Island (Azores) are discussed for the first time. This survey aimed at providing a new insight into the origin and magnitude of GEM in the investigated hydrothermal/volcanic environment and its relation with CO2 release. The distribution of GEM and CO2 emissions over an area of about 0.04 km2 are correlated with soil temperature, and measurements have provided total CO2 and GEM output of 39 t d−1 and 1.8 × 10−6 t d−1, respectively. These results are similar to the emission from currently active volcanic/hydrothermal areas elsewhere, as well as from important non-volcanic areas, such as Sulphur Bank Mercury Mine (California, USA) and Idrija Mercury Mine (Slovenia, EU), pointing out the relevance of diffuse degassing processes at Furnas Volcano. Atmospheric spot measurements in the most vigorous fumarole vents of the geothermal field have shown that the fumarolic GEM contribution (9.2 × 10−7 t d−1) represents a minor fraction of the total (fumarolic + diffusive) GEM output (2.7 × 10−6 t d−1) for the study area of this volcano. Basing upon the integration of the hydrothermal CO2 released and the H2O/CO2 ratio in the fumarolic gas, we have also estimated the thermal energy release associated with diffuse degassing at Furnas Volcano. Our estimates are ∼7.8 MW and 9.8 MW, respectively for Furnas Lake and Furnas Village fumaroles.

The dynamics of mercury near Idrija mercury mine, Slovenia: Horizontal and vertical distributions of total, methyl, and ethyl mercury concentrations in soils

The distributions of the total mercury (T-Hg), methylmercury (MeHg), and ethylmercury (EtHg) concentrations in soil and their relationship to chemical composition of the soil and total organic carbon content (TOC, %) were investigated. Core samples were collected from hill slope on the right and left riverbanks of the Idrija River. Former smelting plant is located on the right bank. The T-Hg average in each of the core samples ranged from 0.25 to 1650 mg kg−1. The vertical T-Hg variations in the samples from the left bank showed no significant change with depth. Conversely, the T-Hg varied with depth, with the surface, or layers several centimeters from the surface, tending to show the highest values in the samples from the right bank. Since the right and left bank soils have different chemical compositions, different pathways of mercury delivery into soils were suggested. The MeHg and EtHg concentrations ranged from n.d. (not detected) to 444 μg kg−1 and n.d. to 17.4 μg kg−1, respectively. The vertical variations of MeHg and EtHg were similar to those of TOC, except for the near-surface layers containing TOC greater than 20%. These results suggest that the decomposition of organic matter is closely related to organic mercury formation.

Controls on microbial mercury transformations in contaminated sediments downstream of the Idrija mercury mine (West Slovenia) to the Gulf of Trieste (northern Adriatic)

Concentrations and transformations of mercury were measured in river, estuarine, and marine sediments to determine factors affecting the fate of mercury entering the northern Adriatic Sea. Radiotracer methodology was used to compare rates of mercury methylation (203Hg), MeHg demethylation (14C), and sulfate reduction (35S) in sediment depth profiles to concentrations of total and dissolved mercury species in the lower freshwater region of the Isonzo River, the coastal lagoons, and in the Gulf of Trieste, northern Adriatic Sea. Mercury was readily methylated and demethylated in all sediments, but the relative activity of these processes varied greatly with location. Methylation activity increased greatly from freshwater to the marine regions; however, demethylation was extremely high in the estuarine and lagoon sites. Ratios of methylation to demethylation were low in these coastal sites but increased further offshore in the gulf, which agreed with increased ratios of MeHg to total Hg (%MeHg) in gulf sediments. Comparisons of microbial activities indicated that sulfate reduction strongly controlled both methylation and demethylation. However, Hg methylation in coastal lagoon sediments was controlled by rapid demethylation and the bioavailability of Hg that was affected by Hg adsorption and precipitation. Methylation in offshore marine sites correlated with sulfate reduction but not the partitioning of Hg between pore water and solid phases. The decrease in sulfide production offshore exacerbated Hg methylation. The freshwater to marine gradient in the Idrija/Soca/Isonzo/Adriatic region is dynamic, exhibiting horizontally variable rates of microbial activities and Hg transformations that create “hot spots” of MeHg accumulation that are controlled differently in each region.

An inter-laboratory comparison of different analytical methods for the determination of monomethylmercury in various soil and sediment samples: A platform for method improvement

An inter-laboratory study was conducted to compare results from different analytical methods for monomethylmercury (MeHg) concentrations in 17 soil and sediment samples. The samples were collected from mercury-contaminated areas, including Minamata Bay and Kagoshima Bay in Japan, the Idrija mercury mine in Slovenia, and an artisanal small-scale gold mining area in Indonesia. The Hg in these samples comes from several different sources: industrial waste from an acetaldehyde production facility, volcanic activity, Hg mining activity, and artisanal and small-scale gold mining activity (ASGM). MeHg concentrations in all the samples were measured in four separate laboratories, using three different determination methods: Kagoshima University (Japan), using high-performance liquid chromatography–chemiluminescence detection (HPLC-CL); National Institute for Minamata Disease (Japan), using gas chromatography–electron capture detection; and Metropolitan Council Environmental Services (USA) and Jozef Stefan Institute (Slovenia), both using alkylation-gas chromatography–atomic fluorescence spectrometry detection. The methods gave comparable MeHg results for most of the samples tested, but for some samples, the results exhibited significant variability depending on the method used. The HPLC-CL method performed poorly when applied to samples with elevated sulfur concentrations, producing MeHg concentrations that were much lower than those from the other methods. Additional analytical work demonstrated the elimination of this sulfur interference when the method was modified to bind sulfur prior to the analytical step by using Hg2+ as a masking agent. These results demonstrate the value of laboratory intercomparison exercises in contributing to the improvement of analytical methods.

Distribution pattern of mercury in the Slovenian soil: Geochemical mapping based on multiple geochemical datasets

A regional geochemical survey was conducted, covering the entire territory of Slovenia. Medium-density soil sampling was performed in a 5×5km grid, mercury concentrations were analysed and a map of mercury spatial distribution was constructed. The determined mercury concentrations revealed an important difference between the western and the eastern parts of the country. A huge anomaly in the western part is the consequence of environmental contamination due to the 500-year history of mining and ore processing in the Idrija mercury mine and partly due to Hg containing rocks on outcrops. Slightly elevated Hg concentrations revealed in the Ljubljana-Kranj and Celje basins indicate urban pollution due to industry, traffic and the use of mercury-containing products. It was established that, besides anthropogenic impacts, lithological and climatic characteristics that determine the type of soil also influence the distribution of mercury in soils. The data were compared to a previously conducted low-density geochemical survey (sampling grid 25×25km, n=54) and to the regional geochemical data set supplemented by local high-density sampling data (irregular grid, n=2835). Comparing high-, medium- and low-sample density surveys, it was shown that higher sampling density allows the identification and characterization of anthropogenic influences on a local scale, while medium- and low-density sampling reveal general trends in the mercury spatial distribution, but are not appropriate for identifying local contamination in industrial regions and urban areas.

Draft Genome Sequence of the Mercury-Resistant Bacterium Acinetobacter idrijaensis Strain MII, Isolated from a Mine-Impacted Area, Idrija, Slovenia.

We report here the first draft assembly for the genome of Acinetobacter idrijaensis strain MII, isolated from the Idrija mercury mine area (Slovenia). This strain shows a strikingly high tolerance to mercury, and the genome sequence shows genes involved in the mechanisms for heavy metal tolerance pathways and multidrug efflux pumps.

Mercury in food items from the Idrija Mercury Mine area

As a consequence of over 500 years of mining and smelting activities (1490–1995), and of its natural geological occurrence, the soil in the Idrija region is highly contaminated with Hg. In order to assess the present situation regarding the Hg levels in local food samples, concentrations of total mercury (THg) and monomethyl mercury (MeHg) were determined in selected vegetables, mushrooms and fish from the Idrija Hg mine area. Hg levels in the foodstuffs analysed were not very high but were elevated compared to the levels in food from non-contaminated areas. The study showed that THg accumulates in mushrooms (X=5680ng/g dry weight, Min=346ng/g dry weight, Max=17,100 dry weight) and chicory (X=1950ng/g dry weight, Min=86ng/g dry weight, Max=17,100ng/g dry weight). In addition, Se and Cd concentrations were determined by ICP-MS in those vegetable and mushroom species in which the highest Hg levels were found. The levels of Cd and Se were below the threshold levels. Based on data from previous studies, we can conclude that the levels of Hg in food have not diminished significantly during the past 15 years after closure of the Hg mine. Special attention should be given to vegetables such as chicory, representing a local seasonal vegetable eaten frequently.

The distribution of total and methylmercury concentrations in soils near the Idrija mercury mine, Slovenia, and the dependence of the mercury concentrations on the chemical composition and organic carbon levels of the soil

Although the mining activity of the Idrija mine in Slovenia ceased in 1995, a large amount of mining dregs containing high concentrations of mercury remains in the area. The mining dregs were transported with river flow and deposition along the Idrija River. To estimate the dispersion and change in the chemical form of mercury, a total of 28 soil core samples were taken around the river. The individual core samples were separated into layers for the analysis of their chemical composition, carbon contents, total mercury (T-Hg) and methylmercury (MeHg) concentrations. The chemical composition measured by X-ray fluorescence spectrometry was useful to estimate the dispersion of tailings: the fluvial terrace soil had a chemical composition similar to that of the tailings and could be distinguished clearly from the forest soil. The highest T-Hg concentration, 1,100 mg kg−1, was observed in the fluvial terrace soil near the mine. Although the concentration decreased gradually along with distance from the mine, concentrations higher than 200 mg kg−1 of T-Hg were still observed in the fluvial terrace soil approximately 20 km downstream from the mine. In the vertical distribution of T-Hg in the hillslope soil, a higher value was observed in the upper layers, which suggests the recent atmospheric deposition of mercury. The concentration of MeHg was the lowest at the riverside and higher in the hillslope soil, which was the opposite of the T-Hg distribution. The total organic carbon content tracked similarly with the distribution of MeHg and a linear relation with a significantly high correlation coefficient was obtained. The distinction may be related to the different dispersion process of mercury, and the organic carbon contents may be an important factor for MeHg formation.

Environmental geochemistry studies in the area of Idrija mercury mine, Slovenia

Five centuries of mining and processing of mercury ore in the Idrija area have resulted in widespread contamination of different environmental compartments. Environmental impacts on a regional and local scale, caused by atmospheric emissions from the Idrija ore roasting plant, were established in the investigations of mercury spatial distribution in soil and attic dust in 160 km(2) area. Very high values were determined in the Idrijca River valley, and they decrease exponentially with the distance from Idrija. Mercury concentrations in attic dust are higher than in surrounding soils and the attic dust/soil ratio changes with distance. Measurements of mercury in the air confirmed widespread dispersion of mercury and showed highly elevated mercury concentrations around roasting plant and mine ventilation shaft. Beside, systematic monitoring of mercury contents in the stream sediments has demonstrated that huge amounts of mercury are stored in areas where ancient overbank sediments were deposited, and there was no decrease in mercury concentration in active sediments during the last 15 years. Recently, interesting and extremely polluted locations of historical small-scale roasting sites in the Idrija surroundings were discovered. Ongoing geochemical study aims to determine the extreme pollution and significance of these sites for wider contamination of soils and aquatic systems. Presented studies have shown that Hg mining in Idrija caused intense pollution of local and regional environment including the aquatic systems in the Gulf of Trieste, which is seen as the final sink of a major part of the Hg stored in soils and river sediments in the Idrija area.

Distribution and partitioning of mercury in a river catchment impacted by former mercury mining activity

Mercury distribution and partitioning was studied in the River Idrijca system, draining the area of the former Idrija mercury mine, Slovenia. Mercury dynamics were assessed by speciation analysis of mercury in water and river bed sediment samples during a 2-year study at locations on the River Idrijca and its major tributaries. Simultaneously, the influence of some major physico-chemical parameters that influence the fate of mercury in the aquatic environment was investigated. The distribution of mercury species in the River Idrijca catchment indicated contamination from mine tailings distributed in the town of Idrija and erosion of contaminated soils. The partitioning between dissolved and particulate mercury phases in river water was found to be mostly controlled by the variable content of suspended solids resulting from changing hydrological conditions and complexation with various ligands present in river water, among which dissolved organic carbon (DOC) seems to be the most important. Overall results indicate that mercury is transported downstream from the mining area mainly as finely suspended material including colloids rather than in the dissolved phase. This riverine transport occurs mostly during short, but extreme hydro-meteorological conditions when remobilization of mercury from the river bed sediments occurs. A significant part of the mercury particulate phase in water corresponds to cinnabar particles. During its transport, important Hg transformation mechanisms that increase the risk of mercury uptake by biota take place, evidenced by the increase in the relative contribution of reactive mercury (HgR), dissolved gaseous mercury (DGM) and monomethylmercury (MeHg) downstream from the Idrija mine. However, our data revealed relatively low methylation efficiency in this contaminated river system. We attribute this to the site specific physico-chemical conditions responsible for making inorganic mercury unavailable and limiting the capacity of methylating bacteria.

Scopoli's work in the field of mercurialism in light of today's knowledge: Past and present perspectives

The Idrija Mercury Mine (1490-1994) appointed its first physician, Joannes Antonius Scopoli, in 1754. Most of his descriptions of mercurialism are still relevant today. This study highlights Scopoli's observations on the interaction between elemental mercury (Hg degrees ) and alcohol, on the appearance of lung impairment, insomnia, and depressive mood in mercurialism. This presentation is based on Scopoli's experiences presented in his book, De Hydrargyro Idriensi Tentamina (1761), current knowledge, and our own experience acquired through health monitoring of occupational Hg degrees exposure. Some studies have confirmed Scopoli's observation that alcohol enhances mercurialism and his hypothesis that exposure to high Hg degrees concentrations causes serious lung impairment. Neurobiological studies have highlighted the influence of Hg degrees on sleep disorder and depressive mood observed by Scopoli. Although today's knowledge provides new perspectives of Scopoli's work on mercurialism, his work is still very important and can be considered a part of occupational medicine heritage.

Natural, cultural and industrial heritage as a basis for sustainable regional development within the Geopark Idrija project (Slovenia)

The Idrija Municipality, situated in the western part of Slovenia, extends over an area of 294 km2 with around 12,000 inhabitants. The area of Idrija is placed at the crossing of Dinaric and Alpine mountain ranges. This position is the reason for an exceptionally diverse surface with deep gorges, high Karst tablelands and mountain tops. Furthermore, the most important natural feature is Idrija mercury ore deposit which was exploited by the Idrija Mercury Mine Ltd. and was the leading force in the development of the region through centuries. Today, the mine is closed but it left an outstanding cultural and industrial heritage that needs to be conserved for future generations - local people to sustain their identity and for visitors. To present the richness of Idrija region the local authorities have put many efforts into establishment of the Geopark since 2007. In 2009 concrete steps were taken with the inventory, thematic trails, evaluation of geoheritage, educational programs, research thesis, etc. With this project the basis and guidelines for the establishment of the Geopark were set. In 2010, the activities have continued at the Municipality level by setting an organisation structure of the future Geopark. .

Geology of the Šalek valley and the surrounding areas from written sources

In the paper are presented the oldest written records on Natural History, and especially the Earth Sciences concerning the Šalek valley and surroundings, and that are of exceptional cultural heritage value. We translated from archaic German a text by Hacquet from 1784 that discusses the Dobrna hot springs, and supplied it with explanations and comments. Added is the copy of a part of Hacquet's lithohydrographic map with Šalek valley in its centre, and with our geologic explanations. Among the first geologists (geognosts) who studied the Šalek valley the German Keferstein should be mentioned, also author of the first geologic map of Germany, Studer, the well-known Swiss geologist and founder of the Swiss Geologic Survey, and Ami Boué, one of founders of the French Geologic Society. The first modern geologic map of most of the Šalek valley and Dobrna depression was elaborated between 1854 and 1856 by Marko Vincenc Lipold, the first geologist of Slovene origin and for many years the general manager of the Idrija mercury mine. The paper overs also the year 1875 when by drilling through the main lignite seam the rich Velenje coal deposit was recognized. This is considered the starting year of exploitation of the Velenje colliery.

Binding of mercury in soils and attic dust in the Idrija mercury mine area (Slovenia)

Total Hg concentrations and Hg speciation were determined in soils and attic dust in a 160 km2 area around Idrija mercury mine. Attic dust as well as a sample of soil was collected at 100 locations. Mercury phases were separated into cinnabar and non-cinnabar compounds via a thermo-desorption technique. The amount of the non-cinnabar fraction is important since it is potentially bioavailable and results are needed for further risk assessment studies.The concentrations of Hg in attic dust are many times higher than in surrounding soils and the attic dust/soil ratio changes with distance. The highest concentration ratios were identified at the greatest distance from the source of pollution and the lowest close to the source of pollution.This confirms the impact of air emissions on the wider area around Idrija. Furthermore the spatial mercury distribution in the attic dust shows that the influence of atmospheric emissions caused by the Idrija smelter resulted in impacts on the environment on a regional scale. The portions of non-cinnabar compounds increase with distance from the mercury source in both sampling media. Non-cinnabar fractions were found to be enriched in distant areas where fine grained material was deposited. There were two different transport mechanisms of dust particles and gaseous Hg(0) during the mercury production period. Obviously coarse grained particles, with mostly cinnabar-bound Hg settled in the immediate vicinity of the smokestack of the smelter, whereas the fine grained fraction could be dispersed further ahead. This is represented by the percentage of cinnabar-bound Hg in attic dust and soil decreasing with distance from the smelter. Gaseous Hg(0) is probably bound to fine and ultrafine aerosols with longer residence time against deposition. The consequence is that fine grained material with Hg2+ and Hg0 prevails in remote localities and is bound in soils and dust with matrix and organic matter as non-cinnabar mercury compounds.The distributions of mercury species in attic dust and soils along the Idrijca River show that in the region from Idrija to Spodnja Idrija the portions of cinnabar and non-cinnabar are about equal, while in the upper and in the lower Idrijca valley non-cinnabar bound mercury prevails.The applicability of attic dust for tracing the mercury halo in the Idrija area was successfully shown.

The Influence of Long-term Mercury Exposure on Selenium Availability in Tissues: An Evaluation of Data

The precise mechanisms of mercury accumulation and retention are still unclear. Generally, the association of mercury with selenium is used to explain these phenomena. It seems that the presence of coaccumulated endogenous Se can protect cells from the harmful effects of Hg. However, as speculated by some authors, this binding of Se to Hg can also result in a relative deficiency of biologically available Se needed for selenoenzyme syntheses. Deriving from the assumption that Hg deposited in tissues is bound to Se in a 1:1 ratio, the quantity of non-Hg bound Se could be calculated by the difference between the molar contents of the two elements (Se(mol)-Hg(mol)). In this study we applied such an approach to the data from our previous investigation, where Hg and Se concentrations were determined in autopsy samples of mercury exposed retired Idrija mercury mine workers, Idrija residents living in a Hg contaminated environment and a control group with no known Hg exposure from the environment. Based on these data we tried to estimate the influence of Hg exposure on the physiologically available selenium content in selected tissues, particularly endocrine glands and brain tissues. Comparing the calculated values of (Se(mol)- Hg(mol)) it was found that for Idrija residents the values were similar to those of the control group and as expected, diminished values were found in some mercury-loaded organs of retired Idrija miners. It could be speculated that in Idrija residents Hg sequestration of selenium is sufficiently compensated by increased Se levels, but that particularly in active miners and in some organs of retired miners, the activity and/or synthesis of selenoenzymes could be disturbed.

Preface: Recent Findings in Mercury Health Effects

The four articles in this mini-monograph represent a cross-section of results from human studies on mercury exposure and health outcomes presented at the most recent International Conference on Mercury as a Global Pollutant (ICMGP) held 28 June to 2 July 2004 in Ljubljana, Slovenia. The ICGMP provides a needed global forum for the exchange of innovative ideas, and it provides an opportunity to communicate research results to public policy makers, industry experts, and public representatives in order to promote the direct use of scientific and technical data to environmental protection and control. Intense interest in mercury is evident from the recommendations adopted by the European Union Mercury Strategy in June 2005 (European Union 2005); also, a Global Mercury Assessment was approved by the Governing Council of the United Nations Environmental Program in early 2002. The 7th ICMGP was held in Ljubljana, Slovenia, the location of the second largest mercury mine in the world—the Idrija mercury mine. Although the mercury mine was the basis of prosperity of the town of Idrija for five centuries, it also caused extensive contamination of the town and its surroundings, leading to high levels of mercury exposure of the miners and the other inhabitants. The mercury mine was closed in the mid-1980s to avoid further releases of mercury to the environment. Mercury research in Slovenia was initiated by the Jožef Stefan Institute in the early 1960s as a result of environmental and health concerns related to the operation of the mine. Initially, the main goal of the institute was to address the health status of the miners. Studies of the effects of mercury on the environment soon followed, and results have been published widely in the scientific literature. The 7th ICMGP consisted of more than 600 scientific presentations, with nearly 500 participants from more than 40 countries, and covered a wide range of topics including analytical chemistry, biogeochemistry, atmospheric science, health effects, and remediation and policy issues. The conference was sponsored by a several Slovenian institutes, ministries, and businesses, including the Jožef Stefan Institute, Ministry of Education Science and Sport, Ministry of Health, Ministry of the Environment and Physical Planning, Thermo Power plant Sostanj, Salonit Anhovo, Slovenian Tourist Board, Ljubljana Turist Board, Mercury Mine Idrija, Cankarjev Dom. International sponsors included Ina Naftaplin, the U.S. Environmental Protection Agency, the Electric Power Research Institute, Tetra Tech, Inc., Tekran Inc., Oak Ridge National Laboratory , Forschungszentrum Geesthacht GmbH (GKSSl), United Nations Environmental Program, Exponent, Global Environmental Facility/United Nations Development Programme/United National Industrial Development Organization (GEF/UNDP/UNIDO), (EUROCHLOR); National Institute for Minamata Disease, CEBAM Analytical Inc., Lumex, and International Research Development Center of Canada. Information on the 8th International Conference on Mercury as Global Pollutant is available online (http://www.mercury2006.org). Two studies in this mini-monograph address human exposure and outcomes related principally to elemental mercury vapors from past mercury mining operations (Kobal et al. 2006) and current high ambient exposures in China due to mercury mining, ore processing, coal combusion, and chloralkali plant operations (Chen et al. 2006) The other two studies address human exposure to methylmercury that occurred principally via fish consumption (Canual et al. 2006; Spurgeon 2006). Together, these articles provide a cross-section of the highly active area of environmental health research regarding exposure to inorganic and organic mercury and health outcomes. Results of the studies provide counter-intuitive insights into the complexities regarding exposure and health effects. For example, although exposure to extremely high levels of mercury in the 18th century hat-making industry led to the “mad as a hatter” syndrome, relatively long-term, considerably lower exposure in the mercury mining industry does not appear to be directly associated with untoward personality traits. Investigation of interactions in vivo between selenium and mercury pointed to likely protective pathways in humans; this interaction has been previously predicted in vitro. Risk assessment methods generally assume that mercury hair levels directly reflect total mercury intake and most especially methylmercury intake from fish consumption. Results from the study of distinct populations in eastern Canada indicate that a considerable number of additional factors need to be determined and considered. Most important, these results imply that a direct linear relation between hair mercury and methylmercury intake cannot always be assumed. And finally, an evidence-based review of epidemiology studies of in utero methylmercury exposure and child developmental outcomes indicates that because of large uncertainties in both exposure assessment and outcome measures across studies, firm conclusions cannot be reached at this time as to whether there is or is not an effect on child neurobehavioral and developmental outcomes at relatively low levels of exposure.